This invention relates to communication systems. More particularly, it is concerned with communication systems employing a network of switching stages connected in a closed ring.
Ring communication systems generally include a plurality of switching nodes intercoupled in a ring with ring transmission paths interconnecting the nodes for transmitting data from node to node around the ring. Each of the switching nodes is an interface at which data may be coupled onto and off of the ring. Ring switching allows various levels of distributing or decentralizing the logic and physical control of a communication system. Ring switching systems may be structured to provide a distributed switching system in which control is dispersed to the switching stage at each individual switching node. That is, all of the control functions are performed independently and autonomously by the switching stages. Only the timing function for synchronizing the operations of the switching stages is common to all the switching stages.
In ring switching systems of this type, the individual switching stages should have low propagation delay so as to permit a large number of nodes to be incorporated in a ring, thus providing high capacity for the network. The switching stages should independently provide the necessary driving power for transmitting data therefrom both on and off the ring, thus permitting expansion without creating additional load on output devices.